Truss and method of making same

ABSTRACT

Camber is automatically attained in the chords of a truss by means of tensioned tensors and compression members between the top and bottom chords of the truss.

United States Patent [191 Wood et a1.

[ 1 Dec. 18, 1973 TRUSS AND METHOD OF MAKING SAME [75] lnventors: GordonG. Wood, Glen Ellyn; James L. McCabe, Wheaton, both of 111.

[73] Assignee: Woodco Ltd., Glen Ellyn, Ill.

[22] Filed: Dec. 21, 1970 [21] Appl. No.: 100,282

[52] US. Cl. 52/223 R, 29/155 R, 29/446,

52/640, 52/693, 52/741 [51] Int. Cl. E04c 3/10, E04c 5/08 [58] Field ofSearch 52/223, 225, 226,

' [56] References Cited UNlTED STATES PATENTS Leland 52/640 PrimaryExaminer1-1enry C Sutherland Attorney-Donald M, Sell [5 7 ABSTRACTCamber is automatically attained in the chords of a truss by means oftensioned tensors and compression members between the top and bottomchords of the truss.

8 Claims, 13 Drawing Figures PATENTEUUEB 18 ms 3.; 778.946

[\VEYTURS ORDON 6', W000 Mes A. Ma C455 ATTORXE Y5 PATENTEDUEC 18 I915SHEET 2 OF 2 muss AND METHOD OF MAKING SAME This invention relates totruss structure and more particularly concerns the attainment of camberin a unique manner.

Heretofore camber has customarily been attained in trusses by prebendingthe chords and then assembling or at least securing the tension and,where employed, compression members in place. Generally the tensionmembers have been rigid structures fixedly and immovably secured to thechords by various expedients such as special hardware, plates and thelike whereby to hold the chords in the camber to which they wereprebent. This has involved often complex structure, combinations anddevices.

Insofar as we are advised, it has heretofore always been necessary toprecamber the chords in some manner, such as by constructing the chordsto have the desired camber or to place the chords in a fixture or jigduring construction to hold them bent to the desired camber while thetruss is assembled.

According to the present invention, the foregoing and otherdisadvantages, defects, inefficiencies, shortcomings and problems inprior truss structures and methods of constructing the same are overcomeand a new and improved truss and method of making the same are providedas will hereinafter become apparent.

An important object of the present invention is to provide a novel trussstructure.

Another object of the invention is to provide a new and improved methodof making trusses.

A further object of the invention is to provide a novel truss structurewhich automatically attains the desired camber in the truss.

A still further object of the invention is to provide a new and improvedmethod of making trusses wherein the desired camber is attainedautomatically as an incident to effecting assembly of the trusscomponents.

Other objects, features and advantages of the invention will be readilyapparent from the following description of certain preferred embodimentsthereof, taken in conjunction with the accompanying drawings, althoughvariations and modifications may be effected 'without departing from thespirit and scope of the novel concepts embodied in the disclosure, andin which:

FIG. 1 is a generally schematic side elevational view of a trussembodying features of the invention;

FIG. 2 is an enlarged fragmentary top plan view taken substantiallyalong the line IIII of FIG. 1;

FIG. 3 is an enlarged fragmentary vertical sectional detail view takensubstantially along the line .III--III of FIG. 2;

FIG. 4 is a sectional detail view similar to FIG. 3 but showing amodification;

FIG. 4A is a fragmentary vertical sectional view of another modifiedtensor securing means;

FIG. 5 is an enlarged sectional plan view taken substantially along theline V-V of FIG. 1;

FIG. 6 is a top plan view taken substantially in the plane of line Vl-VIof FIG. 3;

FIG. 7 is a fragmentary top plan view of a modified truss structure;while FIG. 8 is a side elevational view of the same;

FIG. 9 is a fragmentary top plan view of another modified arrangement ofthe truss and FIG. 10 is a side elevational view of the same; and

FIGS. 11 and 12 are vectorial diagrams.

We have discovered that camber within a substantial and desirable rangecan be obtained in trusses and more particularly in floor and roofsupporting trusses over any permissible span easily, automatically andwith calculable and duplicatable assurance, by simply assembling withthe top and bottom chords properly related tensioning means andcompression-spacer structure.

In making a truss, the compression-spacer structure is placed betweenthe top and bottom chords, relatively unstretchable but flexibletensioning means are attached to and between the chords to extenddiagonally upwardly toward one end of the truss from one side of thelongitudinal center of the truss and toward the opposite end of thetruss relative to the opposite side of the longitudinal center of thetruss, and the flexible tensioning means are tensioned to effectautomatic cambering of the chords.

By way of example, a truss 15 (FIGS. 1 and 2) having a top beam or chordl7 and a bottom beam or chord 18, comprises compression-spacer structurein the form of upright" load stress-distributing compression members 19between the chords; and flexible tension means in the form of relativelyunstretchable but transversely flexible tensors 20 attached atrespective opposite ends to the chords respectively. At one side of thelongitudinal center of the truss 15, the tensors 20 extend diagonallyupwardly and toward the end of the truss at that side of the center andat the opposite side of the truss the tensors extend diagonally upwardlyand toward the opposite end of the truss. Support for the truss 15 maybe provided by any suitable structure between which it is desired tohave it span, such, for example, as spaced walls, partitions, piers,posts, beams, or the like, 21. In this instance, the truss 15 is shownas top-chord-supported with the opposite end portions of the top chord17 in bearing relation over and on the supports 21 and resting on topplates 22 carried on the supports. In this arrangement, the oppositeends of the lower chord 18 are shorter to clear the upper insideportions of the supports 21, with retainer or antisway bars or blocks 23carried by the supports 21 and closely overlying and secured to thelower chord end portions. However, of course, the truss 15 may be bottomchord supported on the supports 21, and in such case the end portions ofthe bottom chord 18 would be carried in bearing relation on the tops ofthe supports.

Spacing of the vertical compression members I9 along the truss ispredetermined according to the size, length, material, load-carryingrequirements, type of planking or other superstructure to be carried,and like structural characteristics. For example, in trusses especiallysuitable for residential building floors, having a span between theirends of 26 feet to 28 feet with the chords constructed of 2 inchdimension lumber, the compression members 19 may be set about 24 inchesapart and may comprise predetermined lengths of wooden 2 inch dimensionlumber. In such trusses the outside to outside height may be from 15 to1-6 inches. Substantial diminution in height is attainable as comparedto at least some prior structures because the width dimensions of thechords is placed in the horizontal direction.

Although the tensors 20 may take numerous and varied forms, a principalrequirement is that they be relatively unstretchable or at leaststrongly resistant to stretching and that their respective opposite endsbe attached tothe chords 17 and 18, respectively; but that the tensorsbe functionally flexible within parameters suitable to attain thedesired camber in the truss. In one simple, economical construction, thetensors 20 may comprise metal rods. In trusses of the general dimensionsalready mentioned, 5/ 16 inch steel rods have been successfullyemployed. These tensor rods are of a length to extend diagonally fromadjacent to the lower end of each of the compression web members 19 toadjacent the upper end of the next adjacent member 19 in the directionof obliquity of the tensor. A desirable attachment arrangement for therespective opposite ends of the tensor rods 20 comprises forming the endportions to extend respectively angularly from the body of the rod at anangle which will place the end portion on an axis normal to thelongitudinal axis of the chord with which it is to be assembled. Forstandardization, thetensor rods may be provided with equal oppositeterminal portions 24 (FIGS. 3 and 5) which extend on parallel axes butin opposite directions, whereby to be received in and through respectivebores 25 in the chords l7 and 18. For this purpose, the length of thetensor attachment terminals 24 are preferably about the same as thethickness of the chord in each instance. Where the chords are of thesame thickness at top and bottom, the terminals 24 can be of the samelength. Where one of the chords differs in thickness, suitablecomplementary revision as to the length of the terminal 24 to bereceived therethrough may be made.

For wooden chords, means are provided for anchoring the tensorterminals'24 in a manner which will resist compressional deflection ofthe wood at the respective bore 25 due to deflectional stresses imposedby loading of the tensor. For this purpose, deflection-resistingrespective plates 27 (FIGS. 3 and 5) mounted at the inner ends of thebores 25, are thoroughly anchored to the respective chords and providedeflection resistant bearings forthe proximal ends of the terminals 24.In an economical structure, each of the bearing plates 27 may comprisesuitable gauge and hardness cast or stamped metal members dimensioned toprovide a substantial plate area about a central bearing aperture 28through which the terminal 24 is received. For increased bearingsurface, the bearing aperture is extended by means of an integral rigidferrule 29 received within the bore 25 to a substantial length. Anysuitable means may be employed to secure the plates 27 to the respectivechord, such, for example, as sharp tipped drive-in prongs 30 formedintegrally with the inner face of the plate and extending in the samedirection as but preferably slightly shorter than the ferrule 29.Thereby, the plate can be properly oriented with respect to the bore 25by starting the distal end of the ferrule 29 into the bore 25, and theplate then driven home by striking it with a hammer, mallet, press orother driving means to cause holding penetration of the prongs 30 intothe 7 chord member.

To secure the terminals 24 to the respective chords, any suitable meansthat will effectively prevent withdrawal of the terminals underfunctioning loads may be employed. One such means comprises respectivethreaded nuts 31 secured on a suitably threaded distal I end portionarea 33 of the respective terminal (FIG. 3).

to receive the, nut 31 and also desirably at least a metal washer, butpreferably means which will distribute the nut thrust over a relativelywide area about the bore 25 to resist to maximum extent desirable anytendency for the material of the chord to yield under stress of the nutpressure or tension loads that may be imposed on and through the tensors20 in service. For this purpose, respective force distribution plates 34(FIGS. 3 and 6) are provided to engage a substantial area of the outerface of the associated chord about the respective counterbore 32 andprovided with an inset 2S complementary to and received in socketedrelation within the counterbore 32 and of an inside diameter to affordample clearance for a wrench to be engaged with and about the nut 31. Inthe bottom of the inset 35 is provided a bearing aperture 37 forprojection therethrough of the distal end portion of the terminal 24 andequipped with a bearing surface ferrule extension 38 extending into thebore 25. Any suitable means for anchoring the plate 34 may be provided,such as integral sharpened inwardly extending securing prongs 39enabling the plate to be attached by hammering it into anchored positionby suitable driving means.

For conditions involving possibty lower magnitude stresses, attachmentof the tensor terminals 24 to wooden chords may be effected at bothopposite ends in the manner depicted in FIG. 4, wherein thedeflectionload distribution plate 27 is provided simply with a bearing surface 28'about an opening through the plate through which the terminal extends,the bore 25' of the chord l7 (and the chord 18 as well) beingdimensioned to receive the terminal 24 closely. Although the outerdeflectional load distribution plate 34' may have the inset portion 35'received in the socket counterbore 32, the inset is provided merely witha simple bearing aperture 37 through which the distal end portion of theterminal 24 extends for securement purposes. While securement may beaccomplished similarly as shown in FIG. 3 by means of a threaded nut, asimple and effective securing means for the lesser load conditionscomprises one or more inwardly fingered annular disk press nuts 40. Forthis purpose the distal end portion of the terminal 24 is left in itsoriginal cylindrical form so that the inwardly directed biting, grippingfingers of the press nut disk will effect a positive retaining grip. Wefind that these press nuts can be applied in multiples to multiplyproportionately the power of retention of the terminal 24 againstwithdrawal from the respective chord. For example, if one of the pressnuts 40 will withstand a pull of 1,000 lbs. against separation of theterminal 24, two of the nuts will withstand about 2,000 lbs. pull.Instead of a plurality of thinner press nuts, a single heavier gaugepress nut may be employed.

In FIG. 4A is depicted another desirable securing means, having theadvantage that counterboring of the respective chord is avoided andrequiring only the straight through bore 25. This comprises acombination bearing and nut plate or disk 34" having an inwardlyextending integral bearing ferrule 38" which has internal threads 33aretainingly engaging the threads 33 of the terminal 24. For driving thedisk 34" it has peripheral wrench notches 340.

Other types of retaining structures may also be employed whereexpedient, such as pins, weldments, upset heads, and the like.

In making a truss employing the tensor rods 20, the chords 17 and 18 arefirst connected together by securing the terminals 24 of the tensor rodsin the respective preformed bores 25 in the chord with the supplementaryhardware provided by the plates 27 and 34 or 27 and 34', as the case maybe. Initial inside spacing of the chords will be determined by thejuncture bends between the respective terminals and the body of each ofthe tensor rods serving as limiting stops during assembly of thecomponents. By having all of the tensor rods standardized as todimensions the chords 17 and 18 will be in straight parallel relation,as shown in dash outline in FIG. 1, after the tensor rods have all beencompletely assembled therewith. Thereafter the load distributing,compression-spacer web members 19 are assembled with the truss. If nocamber is desired in the truss, the length of the compression members 19will be predetermined to be just equal to the assembled spacing betweenthe inside faces of the chords l7 and 18, with the thickness of theplates 27 serving a snugging function between the ends of the members 19and the chord. If desired, the members 19 may be provided withrespective notches 41 (FIG. 3) to clear the adjacent end portions of thetensor rod bodies, where the particular disposition of the tensors wouldinterfere with proper compression load-supporting function of themembers 19 when fully assembled with the chords.

Where, as is generally the case, camber is desired in the chords l7 andand 18, the compression members 19 are predetermined in length,desirably uniform, to be greater than the initial spacing between thechords l7 and 18 after assembly of the tensors 20 therewith. Then, asthe members 19 are placed in assembly in the truss, the desired camberis automatically attained by virtue of placing the tensors 20 undertension. Since the opposite ends of the tensors 20 are secured in fixedpositions on the respective chords, vectorial forces are developed bythe forcing of the chords apart to cause the upward camber bowing of thechords. The longer the compression members 19 are relative to theinitial spacing between the chords, the greater will be the camber, andthis can be calculated with some degree of accuracy and is attainablerepetitively to meet various design and production standards andrequirements.

To illustrate the vectorial phenomenon, reference may be had to FIGS. 11and 12. FIG. 11 represents the vectoric conditions prevailing where thechords 17 and 18 are in straight parallel relation and the compressionmembers 19 are of the same length as the straight parallel spacingbetween the chords, represented by L. In such condition, pivotingtendency under load with respect to the ends A C of the tensor 20 willbe about the deflection radius represented by the are A C at the pointA. Pivoting of the chord sections A B and B C will be on the arcs A' Band B C, respectively. When the compression member length L is increasedas represented in FIG. 12 while the distances A B, A C and D C remainconstant, the arcs A B and D C, respectively, also remain constant, butthe deflection radius are A C shifts to the opposite point C of thetensor 20 as shown, and the desired camber is attained as indicated.

Numerous and varied practical arrangements of the compression members 19and the tensors 20 may be provided to meet design and load requirements.For example, in the form of FIGS. 1 and 2, the two compression members19 nearest the longitudinal center of the truss 15 are spaced on centersnearly but slightly less than the spacing on centers between thecompression members 19 toward each respective end of the truss from suchcentral compression members. Also, the tensors nearest the ends of thetruss are provided in parallel pairs while the remaining tensorsinwardly therefrom toward the center of the truss are singles. In thisinstance where five tensor sections are provided each way from thecenter, the two sections nearest the ends of the truss comprise a pairof the tensors 20 while the three sections nearest the center in eachhalf of the truss comprise a single tensor. This ratio may, of course,be varied to suit the circumstances, or all of the tensor sections maybe double or even triple or more, or all may be singles, as may be bestsuited for the particular structural application. In this instance,also, it will be noted that all of the compression members 19 areoriented as webs with their width across the axis of the truss.

In FIGS. 7 and 8, the two centermost of the compression members 19 arerelatively close together, and could, if preferred comprise a singlemember of possibly greater transverse dimensions to compensate forsingularity as compared to the plurality of central members. In thisinstance, also, the compression members are oriented with their width inthe direction of the axis of the truss. By thus orienting thecompression members, the anchored ends of the tensors 20 can be locatedin the most desirable relation to the respective axes of the compressionmembers, the ideal being coincident with the compression member axes. Inthis instance it is possible to place the anchored ends at least intransverse alignment with the axes of the compression members andrelatively close thereto. This also facilitates efficient drilling ofthe bores 25 in the top and bottom chords at the same time for uniformquality production. Further, in this arrangement increased loadingcapacity is attained by having the top chord ends of the endmost tensors20 advantageously located as nearly as practicable over the center ofthe end bearing supports for the truss. In this instance respectivecompression members 19a are mounted as transverse webs between therespective opposite endmost portions of the chords l7 and I8. Suitablemeans such as nails 42 may be employed to secure the compression members19 and 1% against displacement relative to the chords.

Another representative example of adaptability of the present inventionis depicted in FIGS. 9 and 10 wherein it will be observed that thetopmost tensors 20 of the top chord supported truss have their upper endterminals located efficiently substantially centered over the support21. To enable this centering, means such as a bearing plate 43 havingtensor clearance grooves 44 may be provided. Thereby the most efficientloading capacity for the truss is attained, especially where themultiple tensor arrangement is employed.

From the foregoing it will be apparent that the present inventiongreatly simplifies the construction of trusses in which camber is adesirable or necessary attribute. While for economy and expediency woodis the structurally acceptable material for many installations, othermaterials may be employed in the chords and/or the compression members,such, for example, as steel, reinforced plastic, aluminum, orcombinations of these and other materials with wood. Other materialsthan rod stock may be found structurally acceptable for the tensors,such as wire or cable in fixed or continuous lengths, or even woodenmembers, as long as functional flexibility is present to enable thechords to camber when the tensors are placed under tension. Tensorsstiffness,'span, and the like. Advantageous versatility and adaptabilityis indicated. Further, according to the principles of the presentinvention the truss height can be substantially reduced as compared toat least many prior constructions .to accomplish the same purposes. itwill be understood that variations and modifications may be effectedwithout departing from the spirit and scope of the novel concepts ofthis invention.

We claim as our invention:

l A method of making a truss comprising assembling top and bottom trusschords in generally parallel relation to one another by securingrelatively unstretchable flexible tension means to and between saidchords to extend diagonally toward one end of the truss at one side ofthe longitudinal center of the truss and toward the opposite end of thetruss at the opposite side of said longitudinal center of the truss, andthereafter inserting stress-distributing spacer structure between saidchords and forcing said chords to a greater than initial spacing therebyautomatically cambering said truss as an incident to its assembly.

2. A method according to claim 1, comprising drilling tensor-anchoringbores in beams to provide said chords, shaping tensor rods withanchoring terminals to provide said tensioning means, securing theanchoring terminals of the rods in said bores, and thereafter assemblingbetween the chords compression members of greater length than theinitial assembled spacing of the chords and tensors to provide saidspacing structure and force the chords apart to automatically attain thecamber of the chords.

3. A method for assembling a truss so that camber is induced as anincident to its assembly comprising (a) joining top and bottom chords ingenerally parallel relation to one another with unstretchable tensormembers which are capable of limited flexure under tension load, thetensor members on each side of the truss center being oppositelydiagonally disposed, (b) then forcing said chords to a spacing greaterthan their initial spacing and flexing said tensor members by theinsertion of compression members therebetween thereby automaticallycambering said truss.

4. A method according to claim 3 wherein said compression members extendbetween said chords with the upper and lower ends of each compressionmember being proximal to the upper and lower ends of adjacent tensormembers.

5. A method according to claim 4 wherein said tensor members are stiffrods having their end portions angled from the main body portionsthereof and secured in bores in said chords.

6. A method according to claim 5, said chords having reinforcingstructure about said tensor member end portions. 1

7. A cambered truss comprising generally parallel cambered upper andlower chords interconnected to and spaced from one another by means ofupright compression members and diagonally disposed elongated metaltension members having their end portions angled from the main bodyportions thereof and being relatively 'unstretchable while capable offlexure under tension at the juncture of the end portions to the mainbody portions thereof, said chords having bores therethrough and havingreinforcing plate means at the entrances and exits of said bores, meanssecuring said plates to said chords, said tension member end portions.

extending into said bores and terminating therein below the outersurfaces of said chords and means anchoring said end portions in saidbores, to said plate means said tension members being of generally equallength, said tension members at each side of the truss center lineextending diagonally upwardly toward the end of the truss nearestthereto and being generally equidistantly spaced from one another, saidcompression members extending between said chords and having their endsengaging said chords proximal to said tension member terminal endportions, said compression members being longer than the normaluncambered vertical distance between said chords, said compressionmembers maintaining said tension members under tension load therebyautomatically maintaining the camber of said truss.

8. A truss according to claim 7, wherein said tension members arerelatively flexible.

1. A method of making a truss comprising assembling top and bottom trusschords in generally parallel relation to one another by securingrelatively unstretchable flexible tension means to and between saidchords to extend diagonally toward one end of the truss at one side ofthe longitudinal center of the truss and toward the opposite end of thetruss at the opposite side of said longitudinal center of the truss, andthereafter inserting stress-distributing spacer structure between saidchords and forcing said chords to a greater than initial spacing therebyautomatically cambering said truss as an incident to its assembly.
 2. Amethod according to claim 1, comprising drilling tensor-anchoring boresin beams to provide said chords, shaping tensor rods with anchoringterminals to provide said tensioning means, securing the anchoringterminals of the rods in said bores, and thereafter assembling betweenthe chordS compression members of greater length than the initialassembled spacing of the chords and tensors to provide said spacingstructure and force the chords apart to automatically attain the camberof the chords.
 3. A method for assembling a truss so that camber isinduced as an incident to its assembly comprising (a) joining top andbottom chords in generally parallel relation to one another withunstretchable tensor members which are capable of limited flexure undertension load, the tensor members on each side of the truss center beingoppositely diagonally disposed, (b) then forcing said chords to aspacing greater than their initial spacing and flexing said tensormembers by the insertion of compression members therebetween therebyautomatically cambering said truss.
 4. A method according to claim 3wherein said compression members extend between said chords with theupper and lower ends of each compression member being proximal to theupper and lower ends of adjacent tensor members.
 5. A method accordingto claim 4 wherein said tensor members are stiff rods having their endportions angled from the main body portions thereof and secured in boresin said chords.
 6. A method according to claim 5, said chords havingreinforcing structure about said tensor member end portions.
 7. Acambered truss comprising generally parallel cambered upper and lowerchords interconnected to and spaced from one another by means of uprightcompression members and diagonally disposed elongated metal tensionmembers having their end portions angled from the main body portionsthereof and being relatively unstretchable while capable of flexureunder tension at the juncture of the end portions to the main bodyportions thereof, said chords having bores therethrough and havingreinforcing plate means at the entrances and exits of said bores, meanssecuring said plates to said chords, said tension member end portionsextending into said bores and terminating therein below the outersurfaces of said chords and means anchoring said end portions in saidbores, to said plate means said tension members being of generally equallength, said tension members at each side of the truss center lineextending diagonally upwardly toward the end of the truss nearestthereto and being generally equidistantly spaced from one another, saidcompression members extending between said chords and having their endsengaging said chords proximal to said tension member terminal endportions, said compression members being longer than the normaluncambered vertical distance between said chords, said compressionmembers maintaining said tension members under tension load therebyautomatically maintaining the camber of said truss.
 8. A truss accordingto claim 7, wherein said tension members are relatively flexible.